Concrete Masonry 09

8/9/2019 Concrete Masonry 09

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Concrete & Masonry

Prof Dave Hughes

Taught by lectures, tutorials, lab,

CALCRETE & design sessions

Assessed by Class test multiple choice week

6/7 (30%)2 hour exam - design exercises

(70%)


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Left school when 16 with 7 OLevels


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Farnborough Technical College OND Engineering (1971)


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Portsmouth Polytechnic BSc (Hons)


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Portsmouth Polytechnic BSc (Hons) (1975)

Surrey University PhD (1982)


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Portsmouth Polytechnic BSc (Hons) (1975)

Surrey University PhD (1982)

Bradford University (1985)First Associate Dean (Learning & Teaching)

Mortars conservation and new build


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Introduction

Tofamiliarise you with concrete and mortar


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What are concrete & mortar?

Composite of

Aggregate

Binder


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Composite of

Aggregate

Binder

Gravel

Crushed Rock

Expanded Clay

Sintered PFA

Blast Furnace Slag

Steel Shot

GlassSea shells

Recycled concrete


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Composite of

Aggregate

Binder

Portland Cement

Calcium Aluminate Cement

B-CSA-F CementHydraulic Lime

Air Lime

Water

PFA

GGBSSilica Fume


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What is concrete?

0

10

20

30

40

50

% by

Volume

CoarseAggFine Agg

Binde

rWater

Voids


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What is mortar?

% byVolume

0

10

20

30

40

50

60

FineAgg

Binder Water Voids


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What are the attractions of concrete?

In-situ or Pre-cast

Two states

Range of finishes

High compressive strength

Can be durable


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What the down-sides of concrete?

Cement can be guaranteed but not concrete

Low tensile strength & toughness

Can lack durability

Natural Hydraulic Lime is variable between

and within source

Lime mortars are more flexible


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So what are the differences betweengood concrete and bad concrete?

Application of know-how since theingredients are the same


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So what are the differences betweengood concrete and bad concrete?

Application of know-how since theingredients are the same

CEMENT & LIME, COMPOSITION,COMPACTION, CURING, COVER, CARE


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Testing of concrete & mortar

Compressive strength

Workability

but durability is more often the key factor

a function of permeability and composition

and very rarely tested for


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Layout of the rest of the module

Ingredients

Fresh concrete

Hardened concrete - mechanical

Hardened concrete - permeation

Hardened concrete - durability

Mix design

Mortars

Masonry units

Design exercises


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Cements and Limes

To present specifications for hydraulic cements

and hydraulic limes

To discuss their hydration and the formation of

microstructure


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Terminology of Cements and Limes

SiO2 S

Al2O

3A

CaO C

Fe2O3 F

SO3 S

H20 H


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Cements

Portland cement -

Tri Calcium Silicate C3S

Di Calcium Silicate C2S

Tri Calcium Aluminate C3A

Tetra Calcium Aluminoferrite C4AF


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History of Cements and Limes

0

10

20

30

40

50

60

1900 1920 1940 1960 1980 2000

C3

S

C2

S


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Manufacture of Portland Cement

Quarrying

Limestone

Clay/Shale

Grinding &

Blending

H2O CO2 Clinker

Pre-heat 850oC 1400oC

Add Gypsum

Grinding


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Manufacture of Lime

Quarrying

Limestone

Crushing850oC

1000oC

CO2 Reaction

Slaking


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Lime, Portland Cement & Pozzolanas%age by wt

NHL PC GGBS PFA CSF

S 15 21 37 48 92

A 1 7 11 26 1

F 1 3 1 10 1

C 60 66 40 2 0Alk 1 1 1 4 3

CH C3S AS glass AS glass S glass

CaCO3 C2S

C2S C3A

C2AS C4AF


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Cement & BS EN 197-1:2000Composition

CEM I Portland cement

CEM II Portland-composite cement

CEM III Blast furnace cement

CEM IV Pozzolanic cement

CEM V Composite cement


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Cement & BS EN 197-1:2000

CEM I Portland cement

95 - 100% clinker


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CEM II Portland-composite cement

65 - 94% clinker plus

6 - 35% GGBS, PFA, limestone dust

6 - 10% CSF

6 - 35% mix of any or all


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CEM III Blast furnace cement


36 - 95% GGBS


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CEM IV Pozzolanic cement


11 - 55% CSF + PFA


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CEM V Composite cement


18 - 50% GGBS + 18 - 50% PFA


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Cement & BS EN 197-1:2000Strength

Strength Compressive Strength (MPa) Initial Set

Class Early strength Standard strength (Mins)

2 days7 days 28 days32.5 N 16 32.5 52.5 75

32.5 R 1042.5 N 10 42.5 62.5

6042.5 R 2052.5 N 20 52.5 45


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Lime & BS EN 459-1:2010

NHL - from a single source of argillaceous or

siliceous limestone with no additions

HL - from a combination of unspecified sources,may contain PC, GGBS, CSF, natural

pozzolana

FL same as HL but must specify contents


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Lime & BS EN 459-1:2001Strength

Strength Strength (MPa)

Class 7 days 28 days

NHL/FL 1 0.5 - 3

NHL/HL/FL 2 2 - 7

NHL/HL/FL 3.5 3.5 - 10

NHL/HL/FL 5 2 5 - 15

All limes to be sound 2 mmSetting in 1 hour 14 days!!!!!!!!!!!!!


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Basic hydration


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Basic hydration

C3A + H > C3AH6C3A + H + C H2> C6A 3H32S

_S_


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Basic hydration

C3A + H + C H2> C6A 3H32

C3S + H > CSH + CH

S_

S_


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Basic hydration

C6A 3H32 > C4A H18

C3A + H > C4AH19C4A H18 & C4AH19 known as AFm

S_

S_

S_


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Basic hydration


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Slower long term reactions

C2S + H > CSH + CH

CH + S > CSH (pozzolanic reaction)


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Physical Structure Development

Water

Vapour

CapillaryAdsorbed

Interlayer

Combined


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Pore Structure

1 - 5 mm Entrapped air

100 m - 1 mm Entrained air

0.01 m - 15 m Capillary voids

< 0.01 m Interlayer or gel voids


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Pore Structure Development


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1 10 100 1000

Porosity

Pore size (nm)

1 d PFA

1 d OPC

6 m OPC

6 m PFA


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Types of PC

LHPC

SRPC

White

RHPC - (CEM 1R)


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Types of PC

LHPC Low C3S, high C2S

SRPC 3.5% C3A

White No or trace C4AF

RHPC - (CEM 1R) High C3S or high SSA


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CALCRETE

Read all of section on cements


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Aggregates

To identify key properties as they affect the

properties of concrete

To describe methods of their determination


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Types of aggregates by density

Heavyweight

(4000 - 8500 kg/m3)

Normal

(2300 - 2500 kg/m3)

Lightweight

(350 - 1800 kg/m3)


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Heavyweight

Normal

Lightweight

Magnetite

Iron shot

Lead shot


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Heavyweight

Normal

Lightweight

Natural Crushed rock

Sand & gravel

Artificial Air cooled slag

Broken brick


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Heavyweight

Normal

Lightweight

Natural Pumice

Expanded

clay or shale

Artificial Furnace clinker

Foamed slag

Sintered PFA


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Strength

Concrete 30 - 80 MPa

Aggregate 70 - 350 MPa


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Factors affecting workability of

concrete

Water content

Aggregate type and grading

Mix proportions

Cement fineness

Admixtures

Oven dry


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Porosity

Air dry

Saturatedsurface dry

Moist

Absorptionor porosity

Free

moisture

content

Total

moisture

content


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Aggregate Type

Shape

Rounded

IrregularAngular

Flaky

ElongatedFlaky and elongated


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Aggregate Type

Texture

Glassy

SmoothGranular

Rough

CrystallineHoneycombed


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Aggregate Grading

Maximum size

Continuous grading


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Aggregate Grading

Sieve Size

% age

passing

Continuous

Gap


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Sieve Analysis

Sieve Wt ret % ret Cum % ret Cum % pass

5.00 0 0 0 100

2.36 32 16 16 84

1.18 40 20 36 640.60 42 21 57 43

0.30 46 23 80 20

0.15 32 16 96 4

Pan 8 4 100 0Total 200


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BS classification - Fine aggregate

Sieve Overall C M F

5.00 89 - 100

2.36 60 - 100 60 - 100 65 - 100 80 - 100

1.18 30 - 100 30 - 90 45 - 100 70 - 100

0.60 15 - 100 15 - 54 25 - 80 55 - 100

0.30 5 - 70 5 - 40 5 - 48 5 - 70

0.15 0 - 15*

* 20% for crushed rock sands


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0

20

40

60

80

100

150 300 600 1.18 2.36 5

BS classification - Fine


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0

20

40

60

80

100

150 300 600 1.18 2.36 5

BS classification - Medium


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BS classification - Coarse

0

20

40

60

80

100

150 300 600 1.18 2.36 5


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BS classification - Coarse aggregate

Sieve 20 mm SS 10 mm SS

37.5 100

20.0 85 - 100

14.0 100

10.0 0 - 25 85 - 100

5.0 0 - 5 0 - 25

2.36 0 - 5


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Impurities

Chlorides

Clay

Organic matter

Unsound particles


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CALCRETE

Read aggregate section for winning and

processing and deleterious materials

Revision0.18


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0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.0010.010.11101001000

Mean Pore Diameter (m)

CumulativePoreVolume(ml/gm)

A

B

C F h


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Concrete - Fresh state

To identify the factors which control properties

of concrete in the fresh state

To be able to modify those properties by use ofadmixtures

To be able to perform standard workability tests

K ti


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Key properties

Fluidity

Compactability

Cohesiveness

Workability is the amount of internal work

required to achieve full compaction

Workability

R i t t fl


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Resistance to flow

Friction & Interference Water lubricated

C it i f b t k bilit t t


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Criteria for robust workability tests

Simple equipment

Easily & quickly performed

Appropriate for range of workability sought

Repeatable

Sl


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Slump

Truncated cone Three equal layers

Rod each layer 25 times Scrape off the surface

300 mm

200 mm

Sl


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Slump

slump cone

rod

concrete

Slump


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Slump

Slump

Ruler

Slump


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Slump

Normal range of slump 50 - 100 mm

Medium workability only

Compacting Factor


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Compacting Factor

Two cones Drop through into cylinder

Weigh W1 Fully compact and fill up

Weigh W2

Compacting Factor


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Compacting Factor

CF = W1 / W2

Normal range 0.70 - 0.95

Low workability with zero

slump

VB


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VB

Slump in cylinder

Apply standard vibration

Normal range 4 -35 seconds

Very Low workability

V i b

r a

t i o

n

Flow Table


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Flow Table

For mortars

Compact in 2 layers

15 jolts, 1 per second

Typically 17 cm though no

standard

Flow

Key factors


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Key factors

Free water content (FWC)

Aggregate & cement fineness (grading)

Aggregate shape and textureAggregate moisture state

Proportions of fine to coarse aggregate

Presence of PFA or CSFTemperature and time

Key factors


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Key factors

Presence of PFA or CSF

Admixtures


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Admixtures

Plasticiser

Super-plasticiser

Retarder

Accelerator

Choice of workability


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Choice of workability

Level Slump CF Use

V Low 0.78 Roads heavy vibration

Low 25 -50 0.85 Roads light vibration

Medium 75 Mass & rc construction

High 125 Piling and dense steel

V High Self-levelling concrete

Practical considerations


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Bleeding


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Bleeding

Plastic settlement

Plastic shrinkage



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Bleeding

Plastic settlement

Plastic shrinkage

Curing



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Curing

Degree of hydration Efficiency of curing

Strength Permeability Degree of hydration



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act ca co s de at o s

Bleeding

Plastic settlement

Plastic shrinkage

Curing

Thermal cracking



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Thermal cracking



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Thermal cracking

Hardened concrete - mechanical


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To describe the factors affecting strength

To be able to undertake standard strength tests

To describe the factors affecting moisture relatedmovements

Concrete - Strength


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g

See CALCRETE for detaiMost specified by compressive strength

100 mm cubes, steel moulds, compacted in

2 layers, 20o

C water cure, 28 days, standardloading rate

Some by indirect tension (flexure or split cylinder)


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Labcrete - RealcreteA li d t


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curing

shape

Failure cones

of restraint

Applied stress

Induced stress


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Factors affecting strength


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Intrinsic

Production related Compaction

External environment

Properties of materials


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Cement

Aggregates

Water

Cement -


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fineness

Properties of materials


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Cement

Aggregates

Water

Mix proportions


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Water/Cement ratio

Coarse/fine aggregate ratio

Water/Cement ratio


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Strength

w/c ratio


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Age70

80


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0

10

20

30

40

50

60

1 10 100 1000

Age

Strength

High

Low

Pozz

Compaction


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1% voids reduces strength by some 5%

Vital to compact until air no longer present butdont over-vibrate and segregate mix

Deformation in concrete


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Short term

Long term

Applied stress

Environmental factors

Deformation in Concrete


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Function of Stiffness

Shrinkage

Creep

Elastic behaviourTangent


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Stress

Strain

Initialtangent

g

Secant

Principally related to

strength



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Shrinkage

Creep


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Shrinkage

Creep

Factors affecting creep


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Same as for shrinkage plus

Initial moisture content

Applied stressStorage temperature

Typical values 0 - 1400

CALCRETE


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Hardened Concrete for revision and exercises

Hardened concrete - permeation


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To differentiate between diffusion and

permeability

To relate these to microstructure

Permeation


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Permeability is the ease of flow of a liquid as aresult of a pressure difference (eg flow through

dam)

Diffusion is the ease of flow of a species as a

result of a concentration difference (eg sulphatesflowing from groundwater)

Sorptivity is the uptake of water by capilliary

action in unsaturated concrete or mortar


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Factors affecting permeation


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Porosity

Pore size distribution

Inter-connectivity of poresTortuosity



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CALCRETE


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See Durability for an alternative explanation

So what are the factors that affect


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Porosity

Pore size distribution

Inter-connectivity of pores

w/c ratio


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Age


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Covercrete and Heartcrete


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H

C

Covercrete and Heartcrete


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H

C

Reinforcing

steel Aggressive

agents

CALCRETE


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Read Durability - Permeability and Pore Structure

Hardened concrete - durability


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To recognise some of the major durability

problems facing concrete

To identify means of combating them by referenc

to appropriate microstructures


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Protection of reinforcement


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Correct cover

High quality covercrete

High alkalinity


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Carbonation

D th


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Depth

Period of exposure

Curing, cement

content, rh

w/c, CO2, temp


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Chloride corrosion


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Marine aggregates

De-icing salt

Sea sprayCaCl2 - accelerator

Chloride corrosion


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Marine aggregates

De-icing salt

Sea spray

CaCl2 - accelerator

Chlorides

Free in solution

Physically absorbedChemically bound

Chloride corrosion

Cl-/OH- >0.6Fe

++

+2Cl

-

= FeCl2


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Cl2, O2H2O

Metal

Fe++

Fe

Anode

OH--

Cathode

Cl-Fe +2Cl = FeCl2FeCl2 + 2H2O = Fe(OH)2 +2HC

2e

Corrosion control


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Permeation properties

Cover

Chloride binding capacityBinder content

Binder type

Curing

Sulphate attack


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AFm + CH + + H > C6A 3H32

Na2SO4 + CH + H > C H2 + 2NaOHMgSO4 + CH + H > C H2 + Mg(OH)2

MgSO4 + CSH + H > C H2 + Mg(OH)2 + SH

S_

S_

S

_

S_

S

_

Solutions


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Low C3A

Permeation properties

CH binding (PFA, GGBS, CSF)

Frost attack


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Frost attack


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Hydraulic pressure

Osmotic pressure

Ice

Water

Solutions


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Drainage

Permeation

Air entrainment

Air entrainment


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Air entrainment


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Alkali Silica Reaction (ASR)

Hi h lk li l l


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High alkali levels

Reactive silica

Water


High alkali levels NaOH KOH Ca(OH)


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High alkali levels

Reactive silica

Water

NaOH, KOH, Ca(OH)2

Na2O equivalent > 0.6%

= Na2O + 0.658 K20


High alkali levels Amorphous silica eg opal


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High alkali levels

Reactive silica

Water

Amorphous silica, eg opal,

volcanic glass

Cherts, siliceous limestone,flint


High alkali levels


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High alkali levels

Reactive silica

Water > 75% relative humidity

Temperature


W t


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Alkali

Water

Gel + water =

expansion

S

AS gel

ASR cracking


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Pop-out Map cracking

Solutions

Non reactive aggregates


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Non reactive aggregates

Low alkali cement

Use of PFA, GGBS, PFA

Remove water


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Masonry


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Masonry

Prof Dave Hughes

Brick types

Clay

C l i Sili t


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Calcium Silicate

Concrete


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Frost


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Soluble salts


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Soluble salts


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Water threat


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Water threat


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Walls


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Freestanding wal


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Retaining wal


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Weepholes in Austria


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Reinforced walls


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Reinforced walls


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Movement joints


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Movement joints


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Movement joints


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Movement joints


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Durability of masonry

Design


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Design

Material specification

BS EN 771-1

Clay

Density

1000 k / 3 (LD) f t t d


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1000 kg/m3 (HD) for un-protected

masonry


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BS EN 771-1

Clay

Durability Frost


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Exposure

F0 Passive

F1 Moderate

F2 Severe

BS EN 771-2

Calcium Silicate

Strength


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7, 7.5, 10, 15, 20 50, 60, 75


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Sands

Principal quality factors

Average particle size


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Range of sizes

Shape

Impurities, particularly clay

Sands

Impurities


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Annex D of BS EN 13139:2002

Concrete vs Mortar sands

60

80

100

g


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0

20

40

0.1 1 10

Sieve Size (mm)

%passin

Premise of mix design

Voids between aggregate particles are

filled with binder


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By way of example

Unrendered external wall, high

saturation


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1: 3 to 4 if using PC:sand mortar

For a finer sand tend towards 1:3 rather than 1:4

to achieve desired workability, strength and

durability

New advances in silo mortar

Low energy for sustainability

Bi d h


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Binder phase

Sand drying


Binder phase

P tl d t i hi h b di d


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Portland cement is high embodied energy

Hydraulic lime is high embodied energy


Sand drying

Kil i ffi i t


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Kilns are inefficient

Lime has potential

CaO + H20 Ca(OH)2


So what binder could be added to

Ca(OH)2 which is low energy?


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ggbs

Context - strength

50

60

70

80

P

Bradford research

M12?


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0

10

20

30

40

50

0.5 1 2 3 4 5 6

Sand:binder ratio

Strength(MP

NHL

OPC

1:2

1:3

M12?

Context - strength

NHL

FL

10

15

PNHL

Bradford research


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0

5

0.5 1 2 3 4 5 6

Sand:binder ratio

Strength(M

NHL

OPC

1:2

1:3

Context - sorptivity

2.0

2.5

3.0

/min0.5)

NHL

NHL

FL

Bradford research


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0.0

0.5

1.0

1.5

0.5 1 2 3 4 5 6

Sand:binder ratio

Sor

ptivity(mm NHL

OPC

1:2

1:3

Context - wvp

2.0E-11

2.5E-11

3.0E-11

Pa-

1)

NHL

NHL

FL

Bradford research


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0.0E+00

5.0E-12

1.0E-11

1.5E-11

0.5 1 2 3 4 5 6

Sand:binder ratio

WV

P(kgm-

2s

-1 NHL

OPC

1:2

1:3


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Realcrete in mortars?

Bricks

Differing capacity to absorb water


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Mortars

Differing capacity to retain water


1840

1850

1860

1870

1880

1890

ensity(kg/m3)


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1800

1810

1820

1830

1840

0 1 2 3 4 5 6 7 8 9 10

Root time (min0.5

)

ODDe


25%

30%

orosity


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15%

20%

0 1 2 3 4 5 6 7 8 9 1

Root time (min0.5

)

Po

Realcrete in mortars?Comp Strength

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Mortar

S ti it


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0 0.5 1 1.5 2 2.5

Sorp of Substrate

Sorptivity

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 0.5 1 1.5 2

Sorp of Substrate

SorpofMortar

Substrate Comp strength

(MPa)

Flex strength

(MPa)

Steel 4.7 1.3



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Steel 4.7 1.3

OD Ibstock 8.1 2.5

OD Blue 5.6 2.1Sat Ibstock 4.6 1.4

Sat Blue 4.4 1.6

Binder NHL 3.5

The End of knowledge acquisition

From next week design sessions to

d l d t di f d i d


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develop understanding of design and

application of knowledge

Documents

Concrete Masonry 09